The use of antibodies in sensitive immunoassays provides a means of detecting carcinogens adducted to DNA. In population studies, monoclonal antibody technology is a useful tool in developing reagents to detect these chemical structures. Using different monoclonal antibodies that detect different epitopes of aflatoxin adducted to DNA, patterns of reactions appear to detect different metabolic products of this carcinogen. Hetero-antibodies for benzo(a)pyrene (BP)-DNA adducts have been used to identify BP adducted to DNA in lymphocytes from individuals who by occupation have been exposed to high levels of these compounds. Serum from these individuals have been found to have antibodies to BP-DNA. Antibodies to BP-DNA have been found in these individuals as well as in individuals with no history of high exposure by occupation. Highest levels were found in some of the high exposure population although there was no correlation among the group indicating different immunologic response to this carcinogen. Antibodies to aflatoxin have also been found in some sera from individuals in high-exposure area (China), as well as from individuals in low-exposure environments (USA). Differences in titers appear to correlate with exposure areas; however, different titers suggest individual variations in these populations. Monoclonal antibodies to tobacco smoke condensate adduct to DNA have been developed.